Since at least the late 1960s, mattress manufacturers have been concerned with fires in mattresses that have been associated with bedroom fires. During this time, some 30,000 bedroom fires were attributed to mattresses as most of the fires were determined to be caused by cigarette ignition of the mattress resulting from people smoking in bed. An additional 22,000 fires were attributed to open flame ignition of the mattress. Given the large number of fires attributed to cigarette smoking, federal standards were introduced in an attempt to limit the spread of fires that originated on a mattress.
In the late 1980s, open flame ignition surpassed cigarette ignition as the main cause of mattress fires. Later it was determined, through several studies, that the primary source of bedroom fires was the burning of bedclothes located on top of the mattress. Furthermore, it was found that the majority of these fires were caused by children playing with ignition sources such as lighters, matches and candles which then ignited the top-of-the-bed accessories such as sheets, blankets and pillows.
As a result of these surveys, studies were conducted to improve the understanding of mattress fires. These studies led to the development of a test apparatus that could accurately and consistently simulate the burning bedclothes ignition source.
The tests involved placing a mattress/foundation on top of a steel twin-sized bed frame which, in turn, rested on a cement fiberboard surface that formed the bottom of a catch pan. A pair of gas burners was designed to mimic the thermal impact of burning bedclothes. One burner was placed so as to impinge on the top of a mattress surface while the second impinges nearby on the mattress side. The flame generated by the side burner was allowed to burn for 50 seconds while the flame from the top burner burned for 70 seconds. The fires generated by these burners were monitored and it was observed that a typical mattress reached flash-over value in approximately three minutes.
As a result of these studies, California established a regulation (Technical Bulletin 603) that required that a fire on a mattress could not exceed 25 mega joules of heat in the first 10 minutes of the fire, or a peak rate of heat release of 200 kW over a 30-minute period. A problem associated with reaching this criterion is that it is difficult to place a fire-retardant barrier on the outside of the mattress as the treatment that allows a barrier to be fire retardant makes the mattress surface hard and uncomfortable to the touch. For this reason, the outer layer of a mattress is typically some type of quilt or ticking material that burns fairly easily and is considered sacrificial material.
In residential bedroom fires, three different types of people are at risk from the fire. The first of these is the person in the room in which the fire originates and is intimate with the fire. This person would normally be someone on the mattress. The second person is in the room in which the fire originates, but is not intimate with the fire. This could be someone sitting in a chair in the bedroom in which the mattress catches fire or a child who started the fire and is hiding behind a dresser. The third person is someone who is not in the room in which the fire originates and is also not intimate with the fire. This would include someone located in another room in the house in which the mattress catches fire.
The regulation promulgated in Technical Bulletin 603 provides a valuable 30-minute window for the people at risk to detect and escape a fire. Furthermore, the low-peak-heat-release limit will substantially delay the growth and intensity of a fire. Combined, these requirements significantly reduce the risk of rapid flashover to other parts of the residence and thus substantially expand the opportunity for consumers to escape a bedroom fire.
By reducing the size and growth rate of a fire, it is possible to reduce bed fire casualties by one-half to two-thirds. This is because extra time to escape the residence is provided, particularly for those individuals who are not intimate with the fire. Furthermore, additional time is also provided for a person on the mattress to escape with only isolated burns, if any.
In practice, mattress manufacturers follow either or both of two approaches to fire risk reduction: (a) reduce the likelihood of sustained ignition and (b) mitigate the consequences of an ignition. To help achieve these goals, typical fire-resistant mattresses have a fire-resistant barrier located near the outer layer of the mattress, with the outer layer being made of a quilt or ticking material. This fire-resistant barrier works most of the time; however, should the barrier fail, there is no way of preventing the fire from spreading rapidly through the mattress to the inner support compartment, thereby causing a flashover and engulfing the entire mattress in flames. For this reason, the ability to slow the spread of fire that has breached the first fire-resistant barrier would be an important improvement in the art.